1. Field of the Invention
The present invention relates to an apparatus for controlling a continuously variable transmission (CVT) used in a vehicle.
2. Description of the Prior Art
A CVT capable of continuously controlling a speed a ratio e(=output side rotational speed/input side rotational speed) is used in a vehicle for a power transmission unit with an excellent specific fuel consumption. A desired engine speed Ne' is set as an engine speed to achieve an output horse power of the engine set as a function of a pedalling amount of an accelerator pedal for example with a minimum fuel consumption, and the CVT is controlled such that an actual engine speed Ne is equalized to the desired engine speed Ne'. In the prior method of controlling the CVT, the speed change of the CVT, i.e. the alteration in the speed ratio e is always effected when there is some deviation between Ne and Ne', while the transmission loss of the CVT is so large during the speed change that drive torque is disadvantageously transmitted. Also, when the actual engine speed Ne is increased to the desired engine speed Ne' in acceleration of a vehicle, it is advantageous from a view point of the specific fuel consumption to fix the speed ratio e for avoiding the increase of the engine output from being absorbed by moment of inertia and accelerate the vehicle with the low engine speed for proper acceleration.